Daniel Lange's blog (Entries tagged as bash)

Keeping IRC nicks active

nospam@example.com (Daniel Lange) — Tue, 18 May 2010 23:50:00 +0200

Typical IRC services usually allow you to register with nickserv and link a number of nicks to a personal account. It's quite common to have nick, nick_ and nick__ as many IRC clients auto-append underscores if the primary nickname is already in use when connecting. Obviously you can set these alternate nicknames to almost anything you like in a decent client.

Some folks also group a "vanity" nickname or two for whatever reason. To keep these active, people do the "nick shuffle" (/nick newnick, /nick oldnick) all the time:

People who forget the occasional nick shuffle may end up losing a grouped nick because it became inactive. While freenode staff try to contact people before dropping linked nicks, there are occasional prunes of "old data" from the services database. And then nobody can really ask upfront.

So before the next big purge comes up, I wrote a small bash script that logs into a nickserv account and cycles through the linked nicks. A few friends and me have used it successfully for many months now.

Grab a copy of keepnick (2.4kB) and drop it into /usr/local/bin.

Keepnick expects to have an accountname, the corresponding password and then a sequence of linked nicks given on its command line.

Something like

/usr/local/bin/keepnick accountname passw0rd linked_nick linked_nick_ vanity_nick MyOtherNick

should work.

For regular use, you need to set up a cron job to call keepnick e.g. every week. So put something like the following script into /etc/cron.weekly/keepnicks_irc or create a corresponding crontab entry for keepnicks_irc if you do not have the convenient cron.* directories set up:

#!/bin/bash
#
# run keepnick for user(s) irc account(s)
# intended to be run from cron, e.g. through /etc/cron.weekly
#

KEEPNICK="/usr/local/bin/keepnick"
# better safe than sorry
PATH="/sbin:/bin:/usr/sbin:/usr/bin:/usr/local/bin"
export PATH

$KEEPNICK accountname1 passw0rd1 linked_nick1 linked_nick1_ linked_nick1__
$KEEPNICK accountname2 passw0rd2 linked_nick1 linked_nick2_ linked_nick2__

You should see keepnick in action now every week like this:

What happens here is that the IRC services package tells you, keepnick has just authenticated to your account and will now shuffle through all nicks you asked it to. The big advantage is that is does this outside of channels, so not annoying any users. The cron job should make sure you don't forget the nick shuffle anymore.

Making sure your bash supports network connections

Stock bash will support network connections but on Debian and old (=pre-karmic) Ubuntu that capability was disabled at compile time.

If you need to check whether your bash is compiled with network support, type cat < /dev/tcp/time.nist.gov/13 into a bash terminal.

In case that gives you a RFC-867 time string, you're all fine. If not, re-compile your bash with --enable-net-redirections.

Now for something more advanced (but entirely optional):

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zip2dir (expand a zip to a directory of the same name)

nospam@example.com (Daniel Lange) — Thu, 30 Jul 2009 23:51:40 +0200

I needed to expand a lot of jars (Java zips) and other zips of various names into directories of the same name for each file. With 6,239 files of which some are jars, some other zips and many xml and other filetypes all not properly identified by a file extension, this gets a bit too much to do manually.

So:
Finding candidates for these is easy with find . -type f.
The file is most probably a zip archive if the first two characters are "PK", good old Phil Katz' signature. A friendly head -c 2 checks that.
All combined with some rudimentary error checking:

#!/bin/bash
# There is little data security here, so know what you're doing.
# All risks in using this code are yours. It moves and deletes files quite stupidly.
# (c) Daniel Lange, 2009, v0.01, released into the public domain
if [ $# -ne 1 ] ; then
echo "Error: $0 expects exactly one argument, a (fully qualified) path/to/a/zipfile"
exit 1
fi
if [ ! -r $1 ] ; then
echo "Error: file does not exist or no read permission on $1"
exit 2
fi
if [ ! -w "$(dirname $1)" ] ; then
echo "Error: cannot write to directory of $1"
exit 3
fi
if [ "$(head -c 2 $1)" == "PK" ] ; then
mv $1 $1.tmp
mkdir -p $1
unzip -d $1 $1.tmp
rm $1.tmp
else echo "$1 is not a zipfile"
fi

Download available here (1KB).

Typical usage:

find . -type f -print0 |xargs --null -n 1 zip2dir

This will expand all zips under the current directory.
Leave the zip2dir out for a dry run (xargs will just print to the tty then). Look at the -exec switch when digging around a bit more into what find can do for you.

Cool, command-line style blog design

nospam@example.com (Daniel Lange) — Wed, 17 Dec 2008 00:30:00 +0100

It's very seldom that a blog design catches my eye.

Screenshot of Pete Hindle's blog

Most common templates for blog systems like Wordpress or Serendipity are very well honed. Usability, accessibility and visual design of these systems and their default templates are are as good as it gets for the time being. Trying to do better usually fails. But Wordpress-CLI, which I found at Pete Hindle's blog manages to create a unique design. It may be inspired on the google shell (gosh) or older incarnations of the concept, e.g. WebCmd, but it is unique because it requires poking and trying stuff to expose the full functionality. A bit like an old school rogue-like game, it inspires playing with it to find out more. And it reminds nicely of command interfaces to BBS systems although the authors chose a syntax to resemble a unix based shell. You can try out different sub-designs at Rob McFarland's site. Obviously, usability still sucks, but it's worth it! Well done. And Pete: Please write some interesting entries in that blog now .

httpdate - set local date and time from a web server

nospam@example.com (Daniel Lange) — Wed, 22 Oct 2008 23:55:13 +0200

While ntp may be a great protocol, I find it quite bloated and slow for the simple purpose of just setting a local date and time to a reference clock. I do not need 20ms accuracy on a notebook's clock . Thus I use(d) rdate for a decade now but the public rdate servers are slowly dying out. So I'm replacing it more and more with htpdate which works quite nicely. It's written in C and a perl alternative is available on the author's site. There is also a forked windows version of it available.

Developing a bit larger bash script (which syncs a few servers), I wondered whether I could realize the time sync part in bash as well.

It's quite possible:

# open a tcp connection to www.google.com
exec 3<>/dev/tcp/www.google.com/80
# say hello HTTP-style
echo -e "GET / HTTP/1.0\n\n">&3
# parse for a Date: line and with a bit of magic throw the date-string at the date command
LC_ALL=C LANG=en date --rfc-2822 --utc -s "$(head <&3 | grep -i "Date: " | sed -e s/Date\:\ //I)"
# close the tcp connection
exec 3<&-

Simple, eh?

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